In one aspect, this invention relates to the extraction of N-methyl-2-pyrrolidone (NMP) from an aqueous medium. In another aspect, this invention relates to the recovery of NMP from an effluent of a process for preparing poly(arylene) sulfide.
The extraction of N-methyl-2-pyrrolidone (NMP) from aqueous solutions and/or slurries with polar organic solvents is known, and has been described in U.S. Pat. Nos. 3,687,907 and 3,697,487. Of particular importance is the extraction of NMP from effluents of a process for making poly(arylene sulfide), in particular poly(phenylene sulfide), also referred to as PPS. PPS process effluents generally are aqueous brines which comprise NaCl, NMP and other organic and inorganic compounds, as has been disclosed in the above-cited patents. A linear aliphatic alcohol, 1-hexanol, has been used as a extractant for NMP, as is disclosed in U.S. Pat. No. 3,687,907. However, there is an ever present need to discover more effective extractants for NMP than 1-hexanol.